A continuous encapsulation process is disclosed in U.S. Pat. No. 3,812,056 wherein liquid-liquid phase separation is performed in a tubular capsule manufacturing conduit having a single material entrance end and a single material exit end. This process is limited by the fact that the capsule manufacturing vehicle must be passed through the conduit under turbulent flow conditions in order to prevent agglomeration of embryomic capsules as they are formed. Also a temperature gradient must be maintained along the conduit in order to enwrap the intended capsule cores with wall material. Encapsulating systems disclosed as being eligible for use in this process include methylated methylol melamine.
A similar continuous encapsulation process is disclosed in U.S. Pat. No. 3,816,331, except that the manufacturing conduit has a plurality of material introduction ports and a single material exit port. Like U.S. Pat. No. 3,812,056, the process of this disclosure requires that the capsule manufacturing vehicle must be passed through the conduit under turbulent flow conditions in order to prevent agglomeration of embryonic capsules as they are formed. Also like U.S. Pat. No. 3,812,056, a temperature gradient must be maintained along the conduit in order to enwrap the intended capsule cores with wall material.
Japanese Patent Disclosure No. 55-124534 relates to a method for continuously manufacturing microcapsules in a multi-stage cascade of reaction vessels utilizing an interfacial polymerization process for capsule wall formation.
A method of encapsulating to produce microcapsules in which the capsule wall material is produced by the acid catalysis of a water-soluble urea-formaldehyde precondensate and a water-soluble melamine-formaldehyde precondensate in the presence of a water-soluble polymer, which is capable of being cross-linked by said precondensates, is disclosed in U.S. Pat. No. 4,105,823. Example VIII relates to the use of this process to produce capsules by a continuous process whereby the capsule manufacturing vehicle flows through a series of hoppers by means of gravity through overflow pipes. The through-put of this process is such that material takes two hours to pass through the system.
A method of encapsulating by an in situ reaction of melamine and formaldehyde and/or polycondensation of monomeric methylol melamine or etherified methylol melamine, or a low molecular weight polymer thereof in the presence of negatively-charged, carboxyl-substituted linear aliphatic hydrocarbon polyelectrolyte material dissolved in an aqueous vehicle is disclosed in U.S. Pat. No. 4,100,103.